Video stop

Help... I'm starting a creation and I got problem with the video player. Sometimes , when I launched video , It's take 2 seconds before starting. And when the video is rolling on and if I launched a second video , the previous vidéo stop until the second one start. I'm using pjpeg and prores 422 codecs,with the same irregular problem.as you will see i did a video player (play stop, rew &pause) I've done the experience with my video player and the normal video player in IZZ with the same problems.